Analytical devices and instruments are used in a number of applications to quantitatively and/or qualitatively analyze a sample of interest. Analytical devices and instruments are often found in laboratories and are sometimes employed within processing operations. As used herein, an analytical device is any device, system or arrangement that is able to receive a sample of interest and provide an indication of some aspect of the sample of interest. Analytical devices include, without limitation, process gas analyzers, NO/NOx analyzers, hydrocarbon analyzers, continuous emission monitoring systems and process gas chromatographs.
Gas chromatographs (GC) rely on precise control of temperature of chromatographic columns, detectors, and support systems. One or more electrical heaters are used to heat a controlled oven, chamber or locally heated zone or substrate (hereinafter oven). Such heaters operate by cycling on/off in a closed loop control system with temperature feedback provided by one or more temperature sensors in or near the oven. Such state of the art oven temperature control systems provide adequate control of a temperature set point (typically +/−0.1° C. or less) for the oven when external ambient conditions are stable. However, it is common for process gas chromatographs to be installed without protection from the ambient environment. Such exposed process gas chromatographs may experience ambient temperature variations from −40° to +60° C. but are still expected to deliver consistent measurement performance across such wide ambient variations.
As the art of process analytic devices has progressed, there is increasing pressure to provide a more precise analytic output even when faced with significant ambient temperature fluctuations.